1. Field of the Invention
The present invention relates generally to data storage devices such as a hard disk drive, and more particularly, to a pivot shaft fixing structure for securing a pivot shaft that rotatably supports an actuator.
2. Description of the Related Art
A hard disk drive (HDD) stores information in a computer system and reads/writes data from/on a rotating disk using a read/write head. The read/write head flies over a recording surface of the rotating disk and is moved to a desired position on the disk by an actuator to perform its function.
FIG. 1 shows a schematic exploded perspective view of a conventional HDD. FIG. 2 shows a partial cross-sectional view of a pivot shaft fixing structure of the conventional HDD of FIG. 1. Referring to FIGS. 1 and 2, a spindle motor 30 and an actuator 40 are mounted on a base member 11 of the HDD. The spindle motor 30 rotates a disk 20, and the actuator 40 moves a read/write head that reads/writes data from/on a desired position of the disk 20,
The actuator 40 includes a pivot shaft 41 that is fixedly installed on the base member 11, a swing arm 42 that is rotatably coupled to the pivot shaft 41, a suspension 43 that is installed on one end portion of the swing arm 42, and a voice coil motor (VCM) 50 that rotates the swing arm 42. The suspension 43 moves a slider with the read/write head thereon across a surface of the disk 20.
The VCM 50 is controlled by a servo control system for rotating the swing arm 42 in a direction according to Fleming's Left Hand Rule due to an interaction between current flowing through a VCM coil 52 at the other end portion of the swing arm 42 and a magnetic field generated by magnets 54 and 56 facing the VCM coil 52. If the disk drive is turned on and the disk 20 begins to rotate, the VCM 50 rotates the swing arm 42 counter clockwise to move the read/write head over the recording surface of the disk 20. On the other hand, if the disk drive is turned off and the disk 20 stops rotating, the VCM 50 rotates the swing arm 42 clockwise to park the read/write head on a ramp 60.
A cover member 12 is secured to the base member 11 with a plurality of cover securing screws 19. The cover member 12 covers and protects components of the HDD including the disk 20, the actuator 40, etc., and prevents dust or humidity from entering the inside of the disk drive. A groove 13 is formed on the cover member 12 to reduce an interval between the disk 20 and the cover member 12 and thus to reduce vibrations of the disk 20.
The pivot shaft 41 may have various structures, and an example of the pivot shaft 41 is illustrated in the cross-sectional view of FIG. 2. Referring to FIG. 2, the pivot shaft 41 includes a first portion 41a fixed to the base member 11 and a second portion 41b screwed to an upper end of the first portion 41a. 
In order to prevent the pivot shaft 41 and the actuator 40 from shaking due to external impacts and vibrations of the disk drive during the operation, the upper and lower ends of the pivot shaft 41 should be fixedly secure. Thus in the prior art, a screw hole 45 is formed through a top surface of the pivot shaft 41 (i.e., through a top surface of the second portion 41b), and a pivot mounting screw 49 is screwed into the screw hole 45 to fix the upper end of the pivot shaft 41 to the cover member 12. The pivot mounting screw 49 is screwed into the screw hole 45 also through a through-hole 15 formed in the cover member 12.
In the HDD of FIGS. 1 and 2, six cover securing screws 19 are used to secure the cover member 12 to the base member 11, and one pivot mounting screw 49 is used to fix the pivot shaft 41 to the cover member 12. Since many screws 19 and 49 are used in assembling the HDD, a long assembly time and high cost are incurred. In addition, metal particles are produced due to friction between metals when the many screws 19 and 49 are tightened or loosened. Such metal particles may scratch the surface of the disk 20 and damage the head, thereby deteriorating the function of the disk drive.
In general, the pivot mounting screw 49 is tightened using an electric screwdriver. If an impact is applied to the actuator 40 while the pivot mounting screw 49 is tightened with the electric screwdriver, the head and the disk 20 may collide with each other. As a result, the function of the head may deteriorate, and the surface of the disk 20 may be damaged. Further, if the torque of the electric screwdriver is not sufficient to tighten the pivot mounting screw 49, the pivot mounting screw 49 is likely to be loosened resulting in shaking of the pivot shaft 41 and the actuator 40.
Furthermore, if the pivot mounting screw 49 is screwed into the screw hole 45 with misalignment, vibrations may occur when the actuator 40 rotates and impact resistance may deteriorate leading to unreliability of the disk drive. In such case of poor insertion, the pivot mounting screw 49 needs to be disassembled from the screw hole 45. Such disassembly produces metal particles contaminating the disk drive. If the pivot mounting screw 49 cannot be disassembled from the screw hole 45 because of poor insertion, the disk drive may no longer be used. Such misalignment and poor insertion may occur if excessive torque is applied to the pivot mounting screw 49 by the electric screwdriver.